/*
 * $Header: /home/cvsroot/RiseNet/src/filters/SetCharacterEncodingFilter.java,v 1.1 2004/02/16
 * 03:24:07 hongxing Exp $ $Revision: 1.2 $ $Date: 2011/01/07 02:00:52 $
 * ==================================================================== The Apache Software License,
 * Version 1.1 Copyright (c) 1999-2001 The Apache Software Foundation. All rights reserved.
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met: 1. Redistributions of source code must retain the
 * above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions
 * in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * 3. The end-user documentation included with the redistribution, if any, must include the
 * following acknowlegement: "This product includes software developed by the Apache Software
 * Foundation (http://www.apache.org/)." Alternately, this acknowlegement may appear in the software
 * itself, if and wherever such third-party acknowlegements normally appear. 4. The names "The
 * Jakarta Project", "Tomcat", and "Apache Software Foundation" must not be used to endorse or
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * ==================================================================== This software consists of
 * voluntary contributions made by many individuals on behalf of the Apache Software Foundation. For
 * more information on the Apache Software Foundation, please see <http://www.apache.org/>.
 * [Additional notices, if required by prior licensing conditions]
 */
package filters;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * <p>
 * Example filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding. Configuration of this filter is based on the
 * following initialization parameters:
 * </p>
 * <ul>
 * <li><strong>encoding </strong>- The character encoding to be configured for
 * this request, either conditionally or unconditionally based on the
 * <code>ignore</code> initialization parameter. This parameter is required, so
 * there is no default.</li>
 * <li><strong>ignore </strong>- If set to "true", any character encoding
 * specified by the client is ignored, and the value returned by the
 * <code>selectEncoding()</code> method is set. If set to "false,
 * <code>selectEncoding()</code> is called <strong>only </strong> if the client
 * has not already specified an encoding. By default, this parameter is set to
 * "true".</li>
 * </ul>
 * <p>
 * Although this filter can be used unchanged, it is also easy to subclass it
 * and make the <code>selectEncoding()</code> method more intelligent about what
 * encoding to choose, based on characteristics of the incoming request (such as
 * the values of the <code>Accept-Language</code> and <code>User-Agent</code>
 * headers, or a value stashed in the current user's session.
 * </p>
 * 
 * @author Craig McClanahan
 * @version $Revision: 1.2 $ $Date: 2011/01/07 02:00:52 $
 */
public class SetCharacterEncodingFilter implements Filter {

	// ----------------------------------------------------- Instance Variables
	/**
	 * The default character encoding to set for requests that pass through this
	 * filter.
	 */
	protected String encoding = null;
	/**
	 * The filter configuration object we are associated with. If this value is
	 * null, this filter instance is not currently configured.
	 */
	protected FilterConfig filterConfig = null;
	/**
	 * Should a character encoding specified by the client be ignored?
	 */
	protected boolean ignore = true;

	// --------------------------------------------------------- Public Methods
	/**
	 * Take this filter out of service.
	 */
	public void destroy() {
		this.encoding = null;
		this.filterConfig = null;
	}

	/**
	 * Select and set (if specified) the character encoding to be used to interpret
	 * request parameters for this request.
	 * 
	 * @param request  The servlet request we are processing
	 * @param response The servlet response we are creating
	 * @param chain    The filter chain we are processing
	 * @exception IOException      if an input/output error occurs
	 * @exception ServletException if a servlet error occurs
	 */
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		// Conditionally select and set the character encoding to be used
		if (ignore || (request.getCharacterEncoding() == null)) {
			String encoding = selectEncoding(request);
			if (encoding != null) {
				request.setCharacterEncoding(this.encoding);
				response.setCharacterEncoding(this.encoding);
			}
		}
		// Pass control on to the next filter
		chain.doFilter(request, response);
	}

	/**
	 * Place this filter into service.
	 * 
	 * @param filterConfig The filter configuration object
	 */
	public void init(FilterConfig filterConfig) {
		this.filterConfig = filterConfig;
		this.encoding = filterConfig.getInitParameter("encoding");
		String value = filterConfig.getInitParameter("ignore");
		if (value == null)
			this.ignore = true;
		else if (value.equalsIgnoreCase("true"))
			this.ignore = true;
		else if (value.equalsIgnoreCase("yes"))
			this.ignore = true;
		else
			this.ignore = false;
	}

	// ------------------------------------------------------ Protected Methods
	/**
	 * Select an appropriate character encoding to be used, based on the
	 * characteristics of the current request and/or filter initialization
	 * parameters. If no character encoding should be set, return <code>null</code>.
	 * <p>
	 * The default implementation unconditionally returns the value configured by
	 * the <strong>encoding </strong> initialization parameter for this filter.
	 * 
	 * @param request The servlet request we are processing
	 */
	protected String selectEncoding(ServletRequest request) {
		request.getLocale();
		return (this.encoding);
	}
}